This instrument was designed for observing both ground and air targets. The eyepieces are inclined 30 degrees to the optical axes of the large 110mm objective lenses, which provide tremendous light-gathering power. The large range of motion in elevation (-20 to +60°) permits air target surveillance or astronomical use. The integral interchangeable filters include blue-green to protect the observer's eyes against laser radiation; light orange to increase contrast under hazy or foggy conditions, and neutral density for observing under brilliant daytime conditions.